Word Origin & History

knock O.E. cnocian (W.Saxon cnucian), likely of imitative origin. Meaning "deprecate, put down" is from 1892. Knockoff "cheap imitation" is from 1966. Knock out "to stun by a blow for a 10-count" in boxing is short for to knock out of time; slang knockout "attractive person" is from 1892. To knock oneself out "make a great effort" is from 1936. Knock-kneed first attested 1774. Command knock it off "stop it" is first recorded 1902. Knocker "door banger" is from 1598; knockers "a woman's breasts" is from 1941. Knock up is 1663 in sense of "arouse by knocking at the door;" however it is little used ...in this sense in Amer.Eng., where the phrase means "get a woman pregnant" (1813), possibly ult. from knock "to copulate with" (1598; cf. slang knocking-shop "brothel," 1860)."Knocked up in the United States, amongst females, the phrase is equivalent to being enciente, so that Englishmen often unconsciously commit themselves when amongst our Yankee cousins." [John Camden Hotten, "The Slang Dictionary," London, 1860]